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Groups > linux.kernel > #1290360
| From | Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH 4.3 31/71] net, scm: fix PaX detected msg_controllen overflow in scm_detach_fds |
| Date | 2015-12-12 21:30 +0100 |
| Message-ID | <qEYXL-6UZ-3@gated-at.bofh.it> (permalink) |
| References | <qEYO5-6QW-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
4.3-stable review patch. If anyone has any objections, please let me know.
------------------
From: Daniel Borkmann <daniel@iogearbox.net>
[ Upstream commit 6900317f5eff0a7070c5936e5383f589e0de7a09 ]
David and HacKurx reported a following/similar size overflow triggered
in a grsecurity kernel, thanks to PaX's gcc size overflow plugin:
(Already fixed in later grsecurity versions by Brad and PaX Team.)
[ 1002.296137] PAX: size overflow detected in function scm_detach_fds net/core/scm.c:314
cicus.202_127 min, count: 4, decl: msg_controllen; num: 0; context: msghdr;
[ 1002.296145] CPU: 0 PID: 3685 Comm: scm_rights_recv Not tainted 4.2.3-grsec+ #7
[ 1002.296149] Hardware name: Apple Inc. MacBookAir5,1/Mac-66F35F19FE2A0D05, [...]
[ 1002.296153] ffffffff81c27366 0000000000000000 ffffffff81c27375 ffffc90007843aa8
[ 1002.296162] ffffffff818129ba 0000000000000000 ffffffff81c27366 ffffc90007843ad8
[ 1002.296169] ffffffff8121f838 fffffffffffffffc fffffffffffffffc ffffc90007843e60
[ 1002.296176] Call Trace:
[ 1002.296190] [<ffffffff818129ba>] dump_stack+0x45/0x57
[ 1002.296200] [<ffffffff8121f838>] report_size_overflow+0x38/0x60
[ 1002.296209] [<ffffffff816a979e>] scm_detach_fds+0x2ce/0x300
[ 1002.296220] [<ffffffff81791899>] unix_stream_read_generic+0x609/0x930
[ 1002.296228] [<ffffffff81791c9f>] unix_stream_recvmsg+0x4f/0x60
[ 1002.296236] [<ffffffff8178dc00>] ? unix_set_peek_off+0x50/0x50
[ 1002.296243] [<ffffffff8168fac7>] sock_recvmsg+0x47/0x60
[ 1002.296248] [<ffffffff81691522>] ___sys_recvmsg+0xe2/0x1e0
[ 1002.296257] [<ffffffff81693496>] __sys_recvmsg+0x46/0x80
[ 1002.296263] [<ffffffff816934fc>] SyS_recvmsg+0x2c/0x40
[ 1002.296271] [<ffffffff8181a3ab>] entry_SYSCALL_64_fastpath+0x12/0x85
Further investigation showed that this can happen when an *odd* number of
fds are being passed over AF_UNIX sockets.
In these cases CMSG_LEN(i * sizeof(int)) and CMSG_SPACE(i * sizeof(int)),
where i is the number of successfully passed fds, differ by 4 bytes due
to the extra CMSG_ALIGN() padding in CMSG_SPACE() to an 8 byte boundary
on 64 bit. The padding is used to align subsequent cmsg headers in the
control buffer.
When the control buffer passed in from the receiver side *lacks* these 4
bytes (e.g. due to buggy/wrong API usage), then msg->msg_controllen will
overflow in scm_detach_fds():
int cmlen = CMSG_LEN(i * sizeof(int)); <--- cmlen w/o tail-padding
err = put_user(SOL_SOCKET, &cm->cmsg_level);
if (!err)
err = put_user(SCM_RIGHTS, &cm->cmsg_type);
if (!err)
err = put_user(cmlen, &cm->cmsg_len);
if (!err) {
cmlen = CMSG_SPACE(i * sizeof(int)); <--- cmlen w/ 4 byte extra tail-padding
msg->msg_control += cmlen;
msg->msg_controllen -= cmlen; <--- iff no tail-padding space here ...
} ... wrap-around
F.e. it will wrap to a length of 18446744073709551612 bytes in case the
receiver passed in msg->msg_controllen of 20 bytes, and the sender
properly transferred 1 fd to the receiver, so that its CMSG_LEN results
in 20 bytes and CMSG_SPACE in 24 bytes.
In case of MSG_CMSG_COMPAT (scm_detach_fds_compat()), I haven't seen an
issue in my tests as alignment seems always on 4 byte boundary. Same
should be in case of native 32 bit, where we end up with 4 byte boundaries
as well.
In practice, passing msg->msg_controllen of 20 to recvmsg() while receiving
a single fd would mean that on successful return, msg->msg_controllen is
being set by the kernel to 24 bytes instead, thus more than the input
buffer advertised. It could f.e. become an issue if such application later
on zeroes or copies the control buffer based on the returned msg->msg_controllen
elsewhere.
Maximum number of fds we can send is a hard upper limit SCM_MAX_FD (253).
Going over the code, it seems like msg->msg_controllen is not being read
after scm_detach_fds() in scm_recv() anymore by the kernel, good!
Relevant recvmsg() handler are unix_dgram_recvmsg() (unix_seqpacket_recvmsg())
and unix_stream_recvmsg(). Both return back to their recvmsg() caller,
and ___sys_recvmsg() places the updated length, that is, new msg_control -
old msg_control pointer into msg->msg_controllen (hence the 24 bytes seen
in the example).
Long time ago, Wei Yongjun fixed something related in commit 1ac70e7ad24a
("[NET]: Fix function put_cmsg() which may cause usr application memory
overflow").
RFC3542, section 20.2. says:
The fields shown as "XX" are possible padding, between the cmsghdr
structure and the data, and between the data and the next cmsghdr
structure, if required by the implementation. While sending an
application may or may not include padding at the end of last
ancillary data in msg_controllen and implementations must accept both
as valid. On receiving a portable application must provide space for
padding at the end of the last ancillary data as implementations may
copy out the padding at the end of the control message buffer and
include it in the received msg_controllen. When recvmsg() is called
if msg_controllen is too small for all the ancillary data items
including any trailing padding after the last item an implementation
may set MSG_CTRUNC.
Since we didn't place MSG_CTRUNC for already quite a long time, just do
the same as in 1ac70e7ad24a to avoid an overflow.
Btw, even man-page author got this wrong :/ See db939c9b26e9 ("cmsg.3: Fix
error in SCM_RIGHTS code sample"). Some people must have copied this (?),
thus it got triggered in the wild (reported several times during boot by
David and HacKurx).
No Fixes tag this time as pre 2002 (that is, pre history tree).
Reported-by: David Sterba <dave@jikos.cz>
Reported-by: HacKurx <hackurx@gmail.com>
Cc: PaX Team <pageexec@freemail.hu>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Cc: Eric Dumazet <edumazet@google.com>
Reviewed-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/core/scm.c | 2 ++
1 file changed, 2 insertions(+)
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -305,6 +305,8 @@ void scm_detach_fds(struct msghdr *msg,
err = put_user(cmlen, &cm->cmsg_len);
if (!err) {
cmlen = CMSG_SPACE(i*sizeof(int));
+ if (msg->msg_controllen < cmlen)
+ cmlen = msg->msg_controllen;
msg->msg_control += cmlen;
msg->msg_controllen -= cmlen;
}
--
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[PATCH 4.3 00/71] 4.3.3-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:20 +0100
[PATCH 4.3 15/71] packet: only allow extra vlan len on ethernet devices Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:20 +0100
[PATCH 4.3 14/71] packet: always probe for transport header Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:20 +0100
[PATCH 4.3 07/71] af-unix: passcred support for sendpage Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:20 +0100
[PATCH 4.3 17/71] packet: fix tpacket_snd max frame len Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:20 +0100
[PATCH 4.3 06/71] unix: avoid use-after-free in ep_remove_wait_queue Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:20 +0100
[PATCH 4.3 02/71] r8169: fix kasan reported skb use-after-free. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:20 +0100
[PATCH 4.3 08/71] ipv6: Avoid creating RTF_CACHE from a rt that is not managed by fib6 tree Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:20 +0100
[PATCH 4.3 12/71] tools/net: Use include/uapi with __EXPORTED_HEADERS__ Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:20 +0100
[PATCH 4.3 09/71] ipv6: Check expire on DST_NOCACHE route Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:20 +0100
[PATCH 4.3 31/71] net, scm: fix PaX detected msg_controllen overflow in scm_detach_fds Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 62/71] debugfs: fix refcount imbalance in start_creating Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 04/71] af_unix: dont append consumed skbs to sk_receive_queue Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 29/71] tcp: fix potential huge kmalloc() calls in TCP_REPAIR Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 25/71] net/ip6_tunnel: fix dst leak Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 03/71] af-unix: fix use-after-free with concurrent readers while splicing Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 24/71] snmp: Remove duplicate OUTMCAST stat increment Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 36/71] tipc: fix error handling of expanding buffer headroom Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
Re: [PATCH 4.3 36/71] tipc: fix error handling of expanding buffer headroom Ben Hutchings <ben@decadent.org.uk> - 2015-12-14 18:50 +0100
Re: [PATCH 4.3 36/71] tipc: fix error handling of expanding buffer headroom Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-15 01:00 +0100
[PATCH 4.3 16/71] packet: infer protocol from ethernet header if unset Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 66/71] ocfs2: fix umask ignored issue Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 64/71] nfs4: resend LAYOUTGET when there is a race that changes the seqid Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 10/71] ipv6: Check rt->dst.from for the DST_NOCACHE route Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 01/71] certs: add .gitignore to stop git nagging about x509_certificate_list Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 52/71] Btrfs: fix race when listing an inodes xattrs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 67/71] block: fix segment split Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 63/71] nfs4: start callback_ident at idr 1 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 65/71] nfs: if we have no valid attrs, then dont declare the attribute cache valid Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 05/71] af_unix: take receive queue lock while appending new skb Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 61/71] nfsd: eliminate sending duplicate and repeated delegations Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 11/71] Revert "ipv6: ndisc: inherit metadata dst when creating ndisc requests" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:30 +0100
[PATCH 4.3 21/71] ip_tunnel: disable preemption when updating per-cpu tstats Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 55/71] ext4 crypto: fix memory leak in ext4_bio_write_page() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 39/71] bpf, array: fix heap out-of-bounds access when updating elements Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 54/71] rbd: dont put snap_context twice in rbd_queue_workfn() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 50/71] Btrfs: fix race leading to incorrect item deletion when dropping extents Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 35/71] broadcom: fix PHY_ID_BCM5481 entry in the id table Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 57/71] ext4: fix potential use after free in __ext4_journal_stop Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 48/71] Btrfs: fix truncation of compressed and inlined extents Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 41/71] net/neighbour: fix crash at dumping device-agnostic proxy entries Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 23/71] net: thunder: Check for driver data in nicvf_remove() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
RE: [PATCH 4.3 23/71] net: thunder: Check for driver data in nicvf_remove() Pavel Fedin <p.fedin@samsung.com> - 2015-12-14 08:20 +0100
Re: [PATCH 4.3 23/71] net: thunder: Check for driver data in nicvf_remove() 'Greg Kroah-Hartman' <gregkh@linuxfoundation.org> - 2015-12-14 15:20 +0100
RE: [PATCH 4.3 23/71] net: thunder: Check for driver data in nicvf_remove() Pavel Fedin <p.fedin@samsung.com> - 2015-12-14 16:00 +0100
[PATCH 4.3 51/71] Btrfs: fix race leading to BUG_ON when running delalloc for nodatacow Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 56/71] ext4 crypto: fix bugs in ext4_encrypted_zeroout() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 47/71] Btrfs: fix file corruption and data loss after cloning inline extents Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 71/71] [media] cobalt: fix Kconfig dependency Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 34/71] vrf: fix double free and memory corruption on register_netdevice failure Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
Re: [PATCH 4.3 34/71] vrf: fix double free and memory corruption on register_netdevice failure Ben Hutchings <ben@decadent.org.uk> - 2015-12-14 18:50 +0100
Re: [PATCH 4.3 34/71] vrf: fix double free and memory corruption on register_netdevice failure David Ahern <dsa@cumulusnetworks.com> - 2015-12-14 20:00 +0100
Re: [PATCH 4.3 34/71] vrf: fix double free and memory corruption on register_netdevice failure Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-15 06:50 +0100
[PATCH 4.3] vrf: Fix memory leak on registration failure in vrf_newlink() Ben Hutchings <ben@decadent.org.uk> - 2015-12-15 16:20 +0100
Re: [PATCH 4.3] vrf: Fix memory leak on registration failure in vrf_newlink() David Miller <davem@davemloft.net> - 2015-12-15 18:50 +0100
[PATCH 4.3 45/71] btrfs: fix resending received snapshot with parent Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 33/71] net: ip6mr: fix static mfc/dev leaks on table destruction Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 40/71] ipv6: add complete rcu protection around np->opt Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 38/71] RDS: fix race condition when sending a message on unbound socket Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 32/71] net: ipmr: fix static mfc/dev leaks on table destruction Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 46/71] btrfs: check unsupported filters in balance arguments Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 53/71] btrfs: fix signed overflows in btrfs_sync_file Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 44/71] net_sched: fix qdisc_tree_decrease_qlen() races Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 58/71] ext4, jbd2: ensure entering into panic after recording an error in superblock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 43/71] openvswitch: fix hangup on vxlan/gre/geneve device deletion Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 19/71] net/mlx5e: Added self loopback prevention Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 42/71] ipv6: sctp: implement sctp_v6_destroy_sock() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 20/71] net/mlx4_core: Fix sleeping while holding spinlock at rem_slave_counters Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 59/71] firewire: ohci: fix JMicron JMB38x IT context discovery Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 37/71] ipv6: distinguish frag queues by device for multicast and link-local packets Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 18/71] sctp: translate host order to network order when setting a hmacid Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 22/71] net: switchdev: fix return code of fdb_dump stub Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 60/71] nfsd: serialize state seqid morphing operations Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:40 +0100
[PATCH 4.3 70/71] ALSA: hda/hdmi - apply Skylake fix-ups to Broxton display codec Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:50 +0100
[PATCH 4.3 27/71] tcp: md5: fix lockdep annotation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:50 +0100
[PATCH 4.3 68/71] ceph: fix message length computation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:50 +0100
[PATCH 4.3 69/71] ALSA: pci: depend on ZONE_DMA Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:50 +0100
[PATCH 4.3 30/71] tcp: initialize tp->copied_seq in case of cross SYN connection Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:50 +0100
[PATCH 4.3 28/71] tcp: disable Fast Open on timeouts after handshake Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-12 21:50 +0100
Re: [PATCH 4.3 00/71] 4.3.3-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2015-12-13 04:10 +0100
Re: [PATCH 4.3 00/71] 4.3.3-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-13 04:50 +0100
Re: [PATCH 4.3 00/71] 4.3.3-stable review Guenter Roeck <linux@roeck-us.net> - 2015-12-13 17:10 +0100
Re: [PATCH 4.3 00/71] 4.3.3-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-12-14 04:30 +0100
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